My crepe myrtle flowered the first year it was planted. It was about 2 metres high when planted about 6 years ago and is now over 3 metres. It has not flowered since that first flowering although it looks healthy and produces magnificent autumn colours. It is planted in the garden but not in full sunlight for the full day. It faces south and is sheltered to some extent from the north, east and west. It was planted by a reputable, experienced and very qualified landscape gardener but does not flower. It has been lightly pruned, once but not in the past three years at least. The soil appears reasonable as other plants like hedge plants and buddleia and grasses 
planted there have all thrived.
